Typical wireless network systems comprise one or more access devices for communication purposes. The users may be communicated with the access device with personal computers or notebook computers via wireless means. Wireless local area networks (WLANs) were originally intended to allow wireless connections to a wired local area network (LAN), such as where premises wiring systems were nonexistent or inadequate to support conventional wired LANS. WLANs are often used to service mobile computing devices, such as laptop computers and personal digital assistants (PDAs). Typically, Access Points (APs) are set to ensure adequate radio coverage throughout the service area of the WLAN, while minimizing the costs associated with the installation of each AP. The APs must be configured to eliminate coverage gaps and to provide adequate coverage.
A wireless transport network is a network comprises a plurality of wirelessly connected devices that are responsible for relaying traffic for associated mobile clients. An example of a wireless transport network is a plurality of IEEE 802.11 capable devices that provide transport service for IEEE 802.11 or Bluetooth capable clients such as laptop computers, PDA (personal digital assistant), and the like. The network can further comprise one or more connections to a wired network through one or multiple edge devices. The edge devices are equipped and capable of both wireless and wired communication. In a wireless transport network, efficient reduction of unnecessary broadcast traffic is critical. The wireless transmission medium (the air) by nature is shared, therefore broadcast is a convenient way of communication in wireless networks for there is no need to transmit multiple times for a multi-destined frame. Once an originator broadcasts a frame to all its neighboring devices, some, if not all, of its neighboring devices will have to relay the frame for other remote devices. For any device that is a neighbor of multiple devices that are responsible for relaying broadcast frames, it receives multiple copies of the same frame. One simple example is once a device sends out a broadcast frame, it immediately receives multiple copies of the identical frame if there are multiple neighboring devices perform relay function for the frame. Unless a filtering method is implemented on the devices, in the worst case one single broadcast frame may be duplicated in an exponential growth fashion and saturate the network and waste device processing time. In the worst case, these frames may loop around the network until the end of their lives.
There is a need to reduce the unnecessary broadcast frames to prevent frame looping, reduce total traffic amount hence preserve network bandwidth, and save device processing effort. Prior art techniques in saving bandwidth on wireless network include software algorithms to select relay nodes for broadcast traffic, and maintaining sequence numbers of frames originated from each device to discard duplicates. U.S. Pat. No. 5,570,366 describes a method to filter frames from a wired network to a wireless access point via configured protocol parameters. Please refer to U.S. Pat. No. 5,570,366 to Baker, et al., “Broadcast/multicast filtering by the bridge-based access point,” filed on May 18, 1995. The patent disclosed a communication systems which include high speed wired local area networks (LANs) and low speed wireless LANs. Many broadcast or multicast messages are forwarded to the wireless LANs that are not required as the mobile terminals. The prior art provides a means and method for each access point maintains a table of parameters for each associated mobile terminal in the connected wireless LAN. The parameters in that table are compared to the parameters in message frames received by the access point (AP) and only those messages having parameters found in the table are put on the wireless LAN. The tables at each access point are maintained by moving table entries from access point to access point. The art disclosed a method to reduce the unnecessary broadcast frame for the AP.
The patent does not teach how to reduce the traffic within the wireless network which includes a plurality of wireless transport devices coupled to thereon.
Please refer to U.S. Pat. No. 6,549,786, R. Y. M. Cheung, “Method and apparatus for connecting a wireless LAN to a wired LAN,” filed on May 25, 1998. The prior art provided a method and a means for providing internetworking services to wireless nodes. The invention provides for an internetworking node which can either directly relay a message from one wireless node to another wireless node, or forward such messages indirectly by first resending them to another such internetworking node which in turn resends the message to the other wireless node. Therefore, the Patent discloses a mechanism to set up a plurality of wireless nodes and a plurality of wired-wireless edge access points to form a local area network. The internetworking devices themselves can communicate through the wireless medium. Preferably, such internetworking devices are interconnected by means of a wired LAN. The internetworking edge access points are used to relay traffic for wireless nodes unless the source and destination pair can communicate with each other directly. The wireless nodes actively select which access point it should be associated with, and determines whether it needs an AP's help to send messages. This addresses only the client-access point architecture and covers only basic connectivity issues.
However, the patent also failed to disclose a method to filter unnecessary broadcast traffic among the wireless transport devices.